Rate factor of an elementary reaction

In an elementary reaction belonging to a given mechanism and involving reaction intermediates, the rate factor is the product of the rate coefficient plus the concentrations of the principal components (reactants or products) involved in this elementary step raised to the power of partial orders. 

In order to illustrate this definition, let us reconsider step [2.Rlb] of the water synthesis reaction. The reactivity of this step is  

The unit of a rate factor depends on the elementary reaction, like a rate coefficient. 

Note 3.4.- The rate factors of a reaction carried out at constant concentrations are independent of time. 

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